The present inventions relate to improvements in well packers used in sealing the annulus between a tubing string and the casing and methods therefore. More particularly, the present invention relates to packers, which can be easily removed from subterranean locations by use of wire line tools.
Well packers are typically installed in wells to provide a seal for the annulus between the production or other tubing and the well casing. Packers have a tubular body sometime called a mandrel with an axial passageway for fluid flow. An expandable seal assembly and an axially operable seal actuator are positioned on the exterior of the typical packer. The packers are designed to be installed and left in the well for an extended period. Packers are connected to a tubing string, lowered into the well and set (installed) by mechanical means such as by pressure actuation of the seal actuators.
Removal of packers has been accomplished by cutting the packer body and allowing the seal assembly to relax (unset). Prior art methods used chemical and mechanical methods to cut through the wall of the packer body at an appropriate location. Problems with these methods included the need for special well service equipment, reliability and costs. Additionally, cutting through the packer allows the tubing string to fall into the well, requiring a subsequent fishing operation.
The present inventions contemplate an improved removal method and packer structure which can be removed using conventional wire line equipment and without allowing the string to fall into the well. The improved packer of the present invention has a tubular body with an exterior seal mechanism operated by an axially expandable actuator. For example, in a pressure-actuated packer, the actuator is an annular piston-cylinder set. In the present invention, an annular stop, preferably a nut, is connected to the packer body and limits axial movement of the axial actuator. A housing with an adjacent chamber substantially surrounds the stop. The stop is designed so that if it is cut axially, it will disengage from the packer body and allow the axial actuator to move which in turn allows the seal assembly to relax or disengage. Although not critical but desirable, the packer also prevents the stop from moving into a troublesome location. Preferably, the packer has internal locating structure such as a shoulder, key, or the like.
According to the improved method of the present inventions, the stop on the packer body is cut by use of a cutter positioned to cause minimal damage to the packer itself A cutter using a focused chemical reaction may be used. Chemical reactions that may be used in accordance with the invention include the application of chemical methods of focused chemical cutting, exothermic cutting, or an explosive charge.
For descriptions of linear cutting focused charges see: for examples, U.S. Pat. No. : 4,498,367; 4,693,181; and 5,501,154, which are incorporated herein for all purposes by reference and have desirable qualities for use in the present inventions. The chemical reaction can be the explosion of a charge arranged in a cutting pattern on a carrier. The carrier can be lowered into the well by wire line and is positioned inside the wire line body adjacent the annular stop. A conventional explosive cutting tool modified for the present use could be used. For example, the type shown in U.S. Pat. No. 5,720,344 could be modified to cut only through the stop, and thereafter used in this application. This patent is likewise incorporated herein for all purposes by reference. Positioning can be accomplished by numerous means such as depth measurement, locating structure in the packer, or the like. Once in proper position, the tool is activated, thereby severing or cutting the annular stop and releasing the packer seal assembly, thus allowing removal. The short axial cut necessary to disengage the stop does not destroy the integrity of the packer body allowing removal of the tubing string packer assembly intact.
For a description of a chemical cutter, see: for examples, U.S. Pat. Nos.: 5,322,118; 4,125,161; and 4,315,797, which are incorporated herein by reference and have desirable qualities adaptable for use in the present inventions. The chemical reaction can be a reaction between a chemical cutting agent and the material to be cut. A modification of a conventional chemical cutting tool could be used. For example, the type of downhole chemical cutter shown in U.S. Pat. No. 5,322,118 could be modified to produce a short axial cut, through the stop and thereafter used in this application. The carrier can be lowered into the well and positioned as described above. Once in the proper position, the chemical cutter is activated and the annular stop is severed or cut. As above, the short axial cut necessary to disengage the stop does not destroy the integrity of the packer body, allowing removal of the tubing string packer assembly intact.
For a description of an exothermic cutter, see: for examples, U.S. Pat. Nos.: 5,000,426 and 4,598,769, which are incorporated herein by reference and have desirable qualities adaptable for use in the present inventions. The chemical reaction used in the inventions can be an exothermic reaction producing a cutting flame directed through a port or nozzle. Again, the carrier can be lowered and positioned as described above in connection with the explosive charge cutter. An exothermic cutter, for example, of the type shown in U.S. Pat. No. 4,598,769, could be modified to cut axially through the stop, and thereafter used in this application. Once correctly positioned, the exothermic cutter is activated and the annular stop is severed or cut. The short axial cut necessary to disengage the stop does not destroy the integrity of the packer body, allowing removal of the tubing string packer assembly intact.